Who is Grandfather from The Age of Wire and String and what is their importance?

Grandfather, also sometimes called Grandover, is the narrator's grandfather. He is mentioned a number of times, but much of these mentions are in passing, and merely identify him as someone in the house during a particular scene in the book. As a character, the grandfather is faceless and almost devoid of personality. Once, the author suggests that the grandfather has some influence over the father in a conversation, but beyond that, the grandfather seems to be nothing more than a benign, occasional presence.